Determine the weight fraction of nitrogen in the mixture thereof with ammonia , if the volume fraction of nitrogen in the mixture is 10%.

given:
φ(N2) = 10 %
find:
ω(N2) -?
Solution:
Vmixture = 100 lit
V(N2) = 10 lit, а V(NН3) = 100 lit – 10 lit= 90 lit
М(N2) = 28 g/mol
М(NН3) = 17 g/mol
Vm= 22,4 l/mol
of ν=m/М  = V/V_m   have
m=(М •V)/V_m   ;m(N₂)=(28 g• 10 lit)/(22,4 l/mol)  =12,5 g;
m=(М •V)/V_m   ;m(NН₃)=(17 g• 90 lit)/(22,4 l/mol)  =68,3 g;
mmixture = 12,5 g  + 68,3g = 80,8 g
ω(N₂)=m(N₂)/m_mixture =(12,5 g)/(80,8 g)  =0,155.
ω(NН₃)=m(NН₃)/m_mixture =(68,3 g)/(80,8 g)  =0,845
Answer:ω(N2)  = 0,155.